Japan’s lower house of parliament has approved legislation that could see troops sent to fight abroad for the first time since the second world war, despite thousands of protesters overnight chanting and holding up placards reading “No War, No Killing”.

A lower house panel approval on Wednesday of the unpopular bills, which would drop a ban on collective self-defence or fighting to defend a friendly country like the United States, sparked a huge demonstration and more are planned.

The protest was reminiscent of those that toppled prime minister Shinzo Abe’s grandfather from the premiership 55 years ago after he rammed a revised US-Japan security pact through parliament.

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Crowds of protesters – organisers said 100,000 – gathered near parliament. Many stayed well into the night, chanting and holding up placards reading “Abe, quit”, “No War, No Killing” and “Scrap the War Bills”.

Protesters were assembling again on Thursday, although rainy weather could dampen the numbers.

The bills will now go to the upper house, and if no vote is taken after 60 days they will be returned to the lower house, where Abe’s coalition can enact them with a two-thirds majority.

Abe says a bolder security stance, welcomed by Washington, is essential to meet new challenges, such as those from a rising China.

“The security situation around Japan is getting tougher,” Abe told reporters after the vote, which was boycotted by the main opposition parties. “These bills are vital to protect the Japanese people’s lives and prevent war.”

Opponents say the revisions could entangle Japan in US-led conflicts around the globe and violate pacifist article 9 of the US-drafted, post-war constitution.

“Opposition to the bill is growing louder,” said opposition Democratic party leader Katsuya Okada just before the vote. “Prime Minister Abe, you should admit you have not obtained the people’s understanding and immediately withdraw the bills.”

Abe, who returned to office in 2012 pledging to bolster Japan’s defences and reboot the economy, has seen his support slip to around 40% on voter doubts about the legislation and other policies, such as a plan to restart nuclear reactors.

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Some analysts have begun to draw parallels to Abe’s grandfather, Nobusuke Kishi, a wartime cabinet minister who was premier from 1957 to 1960 and resigned on 15 July 1960 because of a public furore over the US-Japan security pact.

Other analysts say that although Abe’s ratings will take a hit, he is likely to survive and win re-election in September for another three-year term as leader of his Liberal Democratic party, given weak opposition inside and outside of the party.

“The problem is there don’t seem to be any encouraging signs that the opposition can coordinate so the LDP is likely to get away with it,” said Jeffrey Kingston, director of Asian studies at Temple University’s Japan campus.

But he added: “There is a lot of hubris and arrogance and it will come back to haunt him. He is no longer the Teflon prime minister.”

The changes, reflected in new US-Japan defence cooperation guidelines, will also expand the scope for Japan’s military to provide logistics support to friendly countries, relax limits on peace-keeping operations and make it easier to respond to “grey zone” incidents falling short of war.